Semiconductor light emitting, light concentrating device

ABSTRACT

A semiconductor light emitting light concentrating device is described which has a multiple diffraction ring for collecting and concentrating the light emitted from an LED integrally formed into the electrode at the semiconductor substrate end of the light emitting device.

FIELD OF THE INVENTION

The present invention relates to a semiconductor light emitting lightconcentrating device, and especially to a light emitting diode(hereinafter referred to as "LED") with an attached lens produced by afine-patterning process.

BACKGROUND OF THE INVENTION

FIG. 1 shows a prior art semiconductor light emitting device. Thereference numeral 1 designates a semiconductor light emitting elementwhich is constituted by epitaxial growth layers comprising a p typeindium-phosphorus (hereinafter referred to as "p-InP") semiconductorsubstrate 2, a p-InP buffer layer 3, a p typeindium-gallium-arsenic-phosphorus (hereinafter referred to as"p-InGaAsP") semiconductor clad layer 4, a p-InGaAsP active layer 5, ann-InGaAsP clad layer 6, an n type indium-gallium-arsenic (hereinafterreferred to as "n-InGaAs") semiconductor contact layer 7, an insulatinglayer 8 such as silicon dioxide (SiO₂), and electrodes 9 and 10. In sucha semiconductor element 1, a light emitting region 11 which conducts alight emission is produced at the center portion of the active layer 5.The reference numeral 12 designates a sphere lens for collecting thelight from the semiconductor light emitting element 1. The referencenumeral 13 designates an adhesive for fixing the sphere lens 12 onto thesemiconductor light emitting element 1.

In this prior art semiconductor light emitting device with such aconstruction when a current is injected thereinto from the electrodes 9and 10 light is isotropically radiated from the light emitting region 11of the active layer 5, and it is guided to the outside, collected by thesphere lens 12 attached to the substrate 2. In this semiconductor lightemitting device the conductivity types of the substrate 2 and theepitaxial layers 3 to 7 and the energy band gap thereof are selectedsuch that a current is concentrated on the light emission region 11,that the recombinations of the electron hole pairs occur thereatconcentrately, and that the light generated at the regions from thelight emitting region 11 to the sphere lens 12 can sufficientlypenetrate those layers.

In this prior art semiconductor light emitting device, however, there isa problem that a skill is required for fixing the sphere lens 12 ontothe substrate 2 by the adhesive 13 without soiling the portions otherthan the required portion by the adhesive 13.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improvedsemiconductor light emitting light concentrating device which can beproduced easily.

Other objects and advantages of the present invention will becomeapparent from the detailed description given hereinafter; it should beunderstood, however, that the detailed description and specificembodiment are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

According to the present invention, there is provided a semiconductorlight emitting light concentrating device comprising: a semiconductorlight emitting element; and a light collection multiple diffraction ringfor collecting the light emitted from said semiconductor light emittingelement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing the prior art semiconductorlight emitting device;

FIG. 2 is a cross-sectional view showing a semiconductor light emittingdevice as a first embodiment of the present invention;

FIG. 3 is a plan view showing the light collection multiple diffractionlens 14 of the device of FIG. 2;

FIG. 4 is a cross-sectional view showing a semiconductor light emittingdevice as a second embodiment of the present invention; and

FIG. 5 is a plan view showing another example of the light collectionmultiple diffraction lens 14 of the device of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 shows a first embodiment of the present invention. The samereference numerals are used to designate the same or correspondingelements as those shown in FIG. 1. The reference numeral 14 designates alight collection multiple diffraction ring which, provided integrallywith the semiconductor light emission element 1, effectively functionsas a lens utilizing the diffraction phenomenon of the light. Thismultiple diffraction ring 14 is produced by growing a p-InGaAs epitaxiallayer which has a narrower energy band gap than that of the active layer5 and does not make the light penetrate, and removing unrequiredportions by a fine-patterning process.

FIG. 3 shows a plan view of this light collection multiple diffractionring 14. The radius and the width of each ring is determined by thewavelength of the light to be generated and the distances between thatand the light sourse and between that and the expected position at whichthe light is to be collected. This can be produced by the reduction ofthe original drawing as in producing usual masks, or by a method ofapproximately making a pattern using a Newton ring which utilizes alight interference.

This embodiment with such a construction where the sphere lens 12 in theprior art device is replaced by the light collection multiplediffraction ring 14 operates similarly as the prior art device becausethe multiple diffraction ring 14 has a light collection ability equal tothat of the sphere lens 12. Furthermore, the device requires no work andno skill for fixing the lens because the multiple diffraction ring 14 isproduced by growing an epitaxial layer on the rear surface of thesemiconductor substrate 2 of the semiconductor light emission element 1.

In the above-illustrated embodiment, the light collection multiplediffraction ring 14 is provided integrally with the semiconductor lightemission element 1, but this ring 14 may be produced on the main surfaceof a transparent substrate 15 and fixed at a position apart from thesemiconductor light emission element 1 as shown in FIG. 4.

In the above-illustrated embodiment, the light collection multiplediffraction ring 14 is constituted by an epitaxial layer, but this ringmay be constituted by a metal which, provided at the rear surface of thesemiconductor substrate 2, also functions as an electrode 10 of thesemiconductor light emission element 1. In this case the production ofthe electrode 10 and the light collection multiple diffraction ring 14can be conducted at the same process, thereby reducing the productionprocess. Besides, the light collection multiple diffraction ring 14 maynot also function as an electrode 10, but may be only required to bemade of the same metal as that of the electrode 10 for the purpose ofreducing the production process. Furthermore, the light collectionmultiple diffraction ring 14 may comprise any non-light transparentmaterial other than an epitaxial layer or a metal. For example, the ringmay be produced by ion injecting impurities deeply into thesemiconductor substrate 2 so as to produce recombination centers of highdensity in a multiple ring shape.

Furthermore, in the illustrated embodiment the light collection multiplediffraction ring 14 is provided at the rear surface of the semiconductorlight emission element 1, but ring 14 may be provided at any positionbecause the light is irradiated isotropically from the light emissionregion 11.

In the illustrated embodiment, the light collection multiple diffractionring 14 is produced to have concentric circles whose diameters can bedetermined by calculation, but even a ring having circles deviated fromconcentric circles and diameters deviated from calculated values isexpected to have a light collection function of some degreecorresponding to the degrees of the deviations.

In the illustrated embodiment InP, InGaAsP, InGaAs series semiconductorlight emission devices are described, but the present invention can bealso applied to GaAs or GaAlAs series semiconductor light emissiondevice.

Furthermore, it is desirable that the distance between the lightemission region 11 and the light collection multiple diffraction ring 14should be larger than the limitation in the fine-patterning process ofthe multiple diffraction ring. The alteration of FIG. 4 is advantageousin view of this point because the distance can be freely selected.

FIG. 5 illustrates an alternate form of the diffraction lens 14 whichcan be used in this invention.

As is evident from the foregoing description, according to the presentinvention, a light collection multiple diffraction ring is used insteadof the sphere lens of the prior art device. The light emitting, lightconcentrating device of this invention can be easily produced by afine-patterning process without need for great skill.

What is claimed is:
 1. A semiconductor light emitting and lightconcentrating device comprising:a semiconductor light emitting elementhaving a front surface and a rear surface opposite from said frontsurface; and a light collecting multiple diffraction ring system forcollecting and focusing the light emitted from said semiconductor lightemitting element, wherein said light collecting multiple diffractionring comprises a metal layer fixed to and integral with a first portionof said rear surface of said semiconductor light emitting element, saidmetal layer also being capable of functioning as an electrode of saidsemiconductor light emitting element.
 2. A semiconductor light emittingand light concentrating device according to claim 1, comprising:asemiconductor substrate having a second surface that forms said rearsurface of said semiconductor light emitting element; a plurality ofepitaxial layers including a light emitting region laminated on a firstsurface of said semiconductor substrate opposite from said secondsurface, wherein said plurality of epitaxial layers including the lightemitting region comprises a buffer layer formed on said first surface ofsaid semiconductor substrate, a first clad layer formed on said bufferlayer, an active layer formed on said first clad layer having said lightemitting region provided at substantially a central portion of saidactive layer, a second clad layer formed on said active layer, a contactlayer formed on said second layer and an insulating layer formed on saidcontact layer that forms said first surface, wherein an energy band gapof said light collecting multiple diffraction ring is narrower than anenergy band gap of said active layer; a first electrode affixed to saidinsulating layer; and a second electrode fixed to a remainder of saidfirst portion of the rear surface of said semiconductor light emittingelement.
 3. The semiconductor light emitting and light concentratingdevice of claim 1, wherein said semiconductor light emitting elementcomprises a plurality of epitaxial layers formed from at least onemember of the group consisting of InP, InGaAsP, InGaAs, and GaAlAs. 4.The semiconductor light emitting and light concentrating device of claim2, wherein said semiconductor light emitting element comprises aplurality of epitaxial layers formed from at least one member of thegroup consisting of InP, InGaAsP, InGaAs, GaAs, GaAlAs.
 5. Thesemiconductor light emitting and light concentrating device of claim 2,wherein said semiconductor substrate and said buffer layer comprise InP,said first clad layer, said active layer, and said second clad layercomprise InGaAsP; said contact layer comprises InGaAs; and saidinsulating layer comprises silicon dioxide.
 6. A semiconductor lightemitting and light concentrating device comprising:a semiconductor lightemitting element having a front surface and a rear surface opposite fromsaid front surface; and a light collecting multiple diffraction ringsystem for collecting and focusing the light emitted from saidsemiconductor light emitting element, wherein said light collectingmultiple diffraction ring comprises an epitaxial layer formed on atransparent substrate surface, said diffraction ring being operativelyassociated with, but physically apart from said rear surface of saidsemiconductor light emitting element.
 7. The semiconductor lightemitting and light concentrating device of claim 6, comprising:asemiconductor substrate having a second surface that forms said rearsurface of said semiconductor light emitting element; a plurality ofepitaxial layers including a light emitting region laminated on a firstsurface of said semiconductor substrate opposite from said secondsurface, wherein said plurality of epitaxial layers including the lightemitting region comprises a buffer layer formed on said first surface ofsaid semiconductor substrate, a first clad layer formed on said bufferlayer, an active layer formed on said first clad layer having said lightemitting region provided at substantially a center portion of saidactive layer, a second clad layer formed on said active layer, a contactlayer formed on said second clad layer and an insulating layer formed onsaid contact layer that forms said front surface, wherein an energy bandgap of said light collecting multiple diffraction ring is narrower thanan energy band gap of said active layer; a first electrode affixed tosaid insulating layer; and a second electrode fixed to the rear surfaceof said semiconductor light emitting element.
 8. The semiconductor lightemitting and light concentrating device of claim 7, wherein saidsemiconductor substrate and said buffer layer comprise InP, said firstclad layer, said active layer, and said second clad layer compriseInGaAsP; said contact layer comprises InGaAs; and said insulating layercomprises silicon dioxide.
 9. A combined light emitting and lightconcentrating device product formed by a method comprising:depositing aplurality of epitaxial layers including a light emitting region on afirst surface of a semiconductor substrate wherein a second surface ofsaid substrate opposite from said first surface constitutes a rearsurface of said device and a top surface of said plurality of layersopposite from said rear surface constitutes an upper surface of saidepitaxial layers; depositing a first metal electrode onto a first areaof said rear surface; depositing a second metal electrode onto saidupper surface; and forming integrally on a second area of said rearsurface, a light collecting multiple diffraction ring for collecting andfocusing the light emitted from said light region.